Roomside replaceable fan filter unit

ABSTRACT

Embodiments described herein relate to a method for utilizing a roomside replaceable fan filter unit having an integral aerosol injector ring. The method begins by replacing a used filter from the fan filter unit with a replacement filter from a roomside of the fan filter unit. Air is then pulled into a housing of the replaceable fan filter unit and out through the replacement filter to the roomside by a fan module. Finally, an aerosol challenge is provided at a location adjacent and upstream of the fan module.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional application and claims benefit of U.S. patentapplication Ser. No. 3/795,304 filed Mar. 12, 2013, of which isincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments described herein relate to roomside replaceable fan filterunits. More particularly, embodiments described herein relate to aroomside replaceable fan filter unit with an aerosol injection ring.

2. Description of the Related Art

Cleanrooms are utilized in many industries, for example pharmaceuticalmanufacturing facilities or biotechnology research labs, where cleanspace is a manufacturing or health-related requirement. A plurality offilters, typically mounted in the ceiling of the cleanroom as roomsidereplaceable filter units, are configured to remove particulate from airentering the cleanroom at a predetermined efficiency selected based uponthe cleanliness requirements of the activities performed in thecleanroom.

The performance of the filters disposed in the roomside replaceablefilter units is critical to for providing contaminant-free orhazardous-free air. Therefore, it is necessary to certify theperformance (e.g., leak and/or filtration efficiency) of the filters byfield testing on at least an annual basis to determine whether thefilters are maintaining the proper filter efficiency. The certificationprocess ensures that the filters are meeting predefined operationscriteria and/or standards.

Typically a certification process includes challenging the filters withan upstream aerosol challenge to perform statistically valid tests. Mostcleanrooms are configured to have a common plenum feeding multipleroomside filter units. In order to test one filter, enough aerosol mustbe provided to the entire plenum to have a sufficient uniformconcentration for testing the filter. As such, large quantities ofaerosol are needed to create a uniform concentration of aerosol withinthe plenum. The large quantity of aerosol needed to test a single filteris not only wasteful, but also undesirably loads the interested filtersin communication with the plenum. Additionally, an undesirably highusage of aerosol, a long period of time is required to adequately chargeand stabilize the aerosol concentration within the plenum, whichundesirably reduces the availability of the clean room for normaloperations.

Thus, there is a need for an improved roomside replaceable filter unitand method for testing filters used in the same.

SUMMARY OF THE INVENTION

Embodiments described herein relate to a method for utilizing a roomsidereplaceable fan filter unit having an integral aerosol injector ring.The method begins by replacing a used filter from the fan filter unitwith a replacement filter from a roomside of the fan filter unit. Air isthen pulled into a housing of the replaceable fan filter unit and outthrough the replacement filter to the roomside by a fan module. Finally,an aerosol challenge is provided at a location adjacent and upstream ofthe fan module.

In another embodiment, a method for utilizing a fan module having anintegral aerosol injector ring is provided. The method begins by forcingair through a filter housing with a fan module disposed upstream afilter to the roomside of the filter housing. An aerosol challenge isthen provided at a location adjacent and upstream of a fan blade in thefan module.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a sectional view of one embodiment of a roomside replaceablefan filter unit;

FIG. 2 is a partial sectional view of an alternative embodiment of asealing section of a filter housing;

FIG. 3 is a partial sectional view of an alternative location for a fanmodule of a roomside replaceable fan filter unit;

FIG. 4 is a top view of one embodiment of an aerosol injector; and

FIG. 5 is a flow diagram of one embodiment of a method for utilizing aroomside replaceable fan filter unit having an integral aerosolinjection ring.

To facilitate understanding, identical reference numerals have beenused, wherever possible, to designate identical elements that are commonto the figures. It is contemplated that elements of one embodiment maybe beneficially incorporated in other embodiments without furtherrecitation.

DETAILED DESCRIPTION

FIG. 1 depicts a sectional view of one embodiment of a roomsidereplaceable fan filter unit (fan filter unit 100) having a fan module106 and an aerosol injector 108 integrated into a single unit that maybe installed in a structure 170, such as a ceiling, wall or floor of aroom, a machine enclosure, mini-environment or other surface bounding anarea requiring delivery of filtered air. The integral aerosol injector108 is located to provide aerosol into the airstream upstream of atleast air moving blades of the fan module 106. The location of theintegral aerosol injector 108 advantageously allows a single filter tobe challenged for testing without having to provide aerosol to otherfilters as currently done in conventional applications. The fan filterunit 100 includes a filter housing 102 to which the fan module 106 andaerosol injector 108 are mounted. The filter housing 102 a plurality ofsidewalls 110 and a top wall 112 that define an interior volume 136. Theside of the sidewalls 110 opposite the top wall 112 terminate in afilter receiving aperture 114 configured to receive a replaceable filter104. In one embodiment, the filter 104 may be a high-efficiencyparticulate air (HEPA) filter or an ultra-low penetration air filter, orany other suitable filter. The filter receiving aperture 114 is sized toallow the filter 104 to at least partially enter the housing 102,thereby allowing the filter 104 to be removed and replaced from thehousing 102 as needed. The top wall 122 includes an inlet 134 whichallows airs to enter the interior volume 136 of the filter housing 102prior to flowing through the filter 104 and out of the filter housing102 through the filter receiving aperture 114.

The sidewalls 110 and the top wall 112 of the filter housing 102 aregenerally fabricated from a rigid material, for example a metalmaterial, such as aluminum or stainless steel. Other rigid materialssuitable for fabricating the sidewalls 110 and the top wall 112 of thefilter housing 102 include materials such as plastic, wood-basedproducts, and glass reinforced plastic, among others. The sidewalls 110are generally configured in a polygonal form, such as a square orrectangle. The sidewalls 110 are sealingly coupled together at theirintersections, for example, by welding, riveting, soldering, adhering,bonding, caulking and the like. The top wall 112 is generally coupled tothe sidewalls 110 in a similar fashion to make the filter housing 102leak-tight.

In one embodiment, the sidewalls 110 and/or the top wall 112 includes amounting pad or tab 116 that facilitates coupling the filter housing 102to a supporting structure (not shown) for disposing the fan filter unit100 above a room, such as a cleanroom. In some locations, the tab 116 isrequired as a seismic restraint.

In another embodiment, a flange 118 (shown in phantom) may extendoutwards from the sidewalls 110 to interface with the structure 170. Theflange 118 may be coupled and/or sealed to the structure 170. The flange118 may be caulked or sealed with a gasket to the structure 170.

A sealing element 120 extends from the sidewalls 110 into the interiorvolume 136 adjacent the filter receiving aperture 114. The sealingelement 120 provides a substantially air-tight seal between the filter104 and the housing 102. In one embodiment, the sealing element 120includes a knife edge 122 that is coupled to sidewall 110 by a sealingflange 124. The knife edge 122 and the sealing flange 124 may befabricated from a single piece of material to prevent air by-pass, andmay also be fabricated with the sidewall 110 as a continuous piece ofmaterial as shown in FIG. 1, for example, as an extrusion. The knifeedge 122 is orientated substantially parallel to the sidewalls 110 andis configured to interface with a sealing face 126 disposed at one endthe filter 104 to create an air-tight seal between the filter housing102 and the filter 104 upon installation of the filter 104 into thefilter housing 102. Thus, the sealing element 120 separates the interiorvolume 136 of the filter housing assembly 102 into a plenum 128 definedbetween the sealing element 120 and the top wall 112 that is upstream ofthe filter 104 and a filter receiving portion 130 in which the filter104 mounts. In other words, the filter 104 interfacing with the sealingelement 120 separates the unfiltered air disposed in the plenum 128defined upstream of the filter 104 with the clean, filtered air,downstream of the filter 104.

In the embodiment depicted in FIG. 1, the sealing face 126 includes atrough 132 circumscribing the perimeter of the filter 104. The trough132 is at least partially filled with a gel, such as silicone orpolyurethane gel. As the filter 104 is move into the filter receivingportion 130, the knife edge 122 of the housing 102 penetrates the gel tocreate an air seal between the filter 104 and the filter housing 102.The filter 104 is secured in the filter housing 102 in a position thatensures engagement between the sealing face 126 and sealing element 120by a filter retainer, such as a pawl tab (not shown) mounted to thesealing flange 124. The filter retainer may alternatively be a screw,nut, clip, quarter, turn fastener or other element suitable forreleasably retaining the filter 104 in the housing 102.

FIG. 2 depicts a partial sectional view a housing 200 illustrating analternative sealing element 220 which may be utilized to form the fanfilter unit 100. Sidewalls 210 of the housing 200 are generally similarto the sidewalls 110 described above with reference to FIG. 1. Thesealing element 220 includes a sealing flange 224 that extendsperpendicularly inward from the sidewall 210 to provide a planar gasketseating surface 202. A filter 204 having a gasket 206 disposed on top ofa portion of a sealing face 226 is urged against the sealing flange 224,thereby compressing the gasket 206 against the sealing flange 224 toprovide a seal between the housing 200 and filter 204. It iscontemplated that the gasket 206 may be alternatively coupled to thesealing flange 204 of the housing 200.

Referring back to FIG. 1, the fan module 106 is coupled to the filterhousing 102. In one embodiment, the fan module 106 is mounted at leastpartially or completely inside the interior volume 136 of the filterhousing 102. The fan module 106 is configured to draw air through theinlet 134 of the filter housing 102 and into the plenum 128, the airultimately flowing through the filter 104 and into the room downstreamof the filter 104. The fan module 106 includes a fan 138 and acontroller 140. The fan 138 includes a motor 160 and blades 162 formoving the air. The controller 140 is configured to control theoperational speed of the fan 138 so that the amount of air flowingthrough the filter housing 102 and out the filter 104 may be set asdesired. In the embodiment seen in FIG. 1, the controller 140 is locatedinternally on the filter housing 102. However, it is contemplated thatthe controller 140 may be located in any suitable location, eithercoupled to, or remotely from, the housing 102.

The controller 140 may includes a fan speed adjustment control 164exposed to the roomside of the filter housing 102 so that the speed ofthe fan 138 may be easily set. For example, the fan speed adjustmentcontrol 164, such as a control knob, may sealingly penetrate through thesealing flange 124 in a location accessible between the installed filter104 and the sidewalls 110 of the filter housing 102. It is contemplatedthat the adjustment control 164 may be located in other locations,either attached or remote from the housing 102, and that in someembodiments, the speed of the fan 138 may be set electronically withoutthe use of a manual adjustment (e.g., adjustment control knob 164), forexample, by using a remotely located computing device or other remotecontroller.

In another embodiment, a fan module 306 may be mounted externally on thefilter housing 302 as illustrated in FIG. 3. The fan module 306 isgenerally similar to the fan module 106 described above with referenceto FIG. 1. In one embodiment, at least one of the housing 302 or the fanmodule 306 includes an optional collar 304 that is configured to matewith ductwork (not shown) that provides air to an inlet 334 formedthrough a top wall 312 of the filter housing 302.

Referring back to FIG. 1, the filter housing 102 may optionally includea diffuser plate 142 disposed in the interior volume 136. The diffuserplate 142 is generally a baffle utilized to redirect airflow within theplenum 128. In one embodiment, the diffuser plate 142 is positioned inthe plenum 128 below the fan module 106 and is configured to enhance theuniform distribution of air within the plenum 128 to enhance flowuniformity exiting the filter 104.

The diffuser plate 142 may be fabricated from a metal or plasticmaterial. The diffuser plate 142 may be a solid sheet or may beperforated. The diffuser plate 142 may also be planar, conical, curvedor have another form. In the embodiment depicted in FIG. 1, the diffuserplate 142 includes optional apertures 144 to allow at least some air toflow therethrough.

The aerosol injector 108 is utilized to introduce an aerosol challengewithin the filter housing 102 upstream of the filter 104. The aerosolinjector 108 is positioned upstream of the air moving blades 162 of thefan module 106, for example, on a side of the fan module 106 oppositethe sealing element 120. The aerosol injector 108 may be positionedinside or upstream of the fan module 106. By positioning the aerosolinjector 108 upstream of the air moving blades 162 of the fan module106, the blades 162 of the fan module 106 contribute to uniformly mixingthe aerosol in the air entering the plenum 128, thereby allowing asmaller plenum 128 and in some cases, eliminating the need for diffuserplate 142, which allows smaller housing side walls 210, thereby reducingthe size and cost of the filter housing 102. Additionally, as each fanfilter unit 100 has its own aerosol injector 108, a single filter may bechallenged for testing without having to provide aerosol to otherfilters as currently done in plenum ceiling applications, therebyproviding a significant reduction in the amount of aerosol utilized andwithout unnecessarily loading filters not currently undergoing test withaerosol which reduces filter life.

The aerosol injector 108 includes one or more ports or nozzles (shown as402 in FIG. 4) which are positioned to dispense aerosol into theairstream entering the housing 102 through the fan module 106. In oneembodiment, the aerosol injector 108 includes a tube 168 positionedinside the filter housing 102 between the inlet 134 and the fan module106. In one embodiment depicted in FIGS. 1 and 4, the aerosol injector108 is tube 168 formed in a ring and having a plurality of ports 402. Inone embodiment, the ports 402 are distributed around the tube 168, forexample in a polar array. This beneficially provides a uniformdistribution of the aerosol through the ports 402 and into the filterhousing 102. The ports 402 formed in the aerosol injector 108 have anorientation which directs a spray 404 of aerosol into the filter housing102 such that the spray is directed into the airstream rather thanagainst a solid surface. In one embodiment, the ports 402 are orientedat an inward angle (e.g., towards the centerline of the inlet 134 of thefilter housing 102), as shown in FIG. 4. However, in other embodiments,the ports 402 may be oriented at an upward, downward or outward angle.The fan module 106 moves the aerosol laden air into the plenum 128. Asdiscussed above, the action of the blades 162 of the fan module 106,along with the optional diffuser plate 142 and/or other baffles provideadequate aerosol mixing of the aerosol laden air so that filterleak-testing may be performed. In one example, the fan module 106provides sufficient mixing to allow ANSI or IEST leak-testing protocolsto be performed, which will be discussed below further in detail.

An aerosol delivery tube 146 is routed through the plenum 128 of thefilter housing 102. The aerosol delivery tube 146 is coupled to theaerosol injector 108. The aerosol delivery tube 146 terminates at anaerosol access port 150 accessible from the roomside, e.g., filterreceiving aperture side, of the housing 102. In one embodiment, theaerosol access port 150 extends through the sealing flange 124 of thehousing 102. The aerosol access port 150 is utilized to connect theaerosol injector 108 to an aerosol generator 148. It is contemplated,however, that the aerosol access port 150 may be positioned on otherparts of the filter housing 102. The aerosol access port 150 isgenerally sealable, either through an internal check valve or with astopper 252, as illustrated removed from the port 150 in FIG. 2. Theaerosol generator 148 is utilized to supply an aerosol challenge to theupstream side of the filter 104 in the plenum 128 to enable astatistically valid test of the filter 104.

Injecting aerosol directly at the inlet 134 into the fan filter unit 100advantageously reduces the amount of aerosol required for field testing,increases the uniformity of aerosol distribution adjacent the filter,and also allows field certifying technicians to accurately meetleak-testing protocols from roomside of the housing 102. Since theaerosol is provided to the aerosol access port 150 of a specific fanfilter unit 100, each fan filter unit 100 can be tested individuallyfrom the roomside of the housing 102 without interrupting the normaloperation of adjacent fan filter units 100. In one embodiment, theaerosol is injected between the between the inlet 134 and the fan module106 on upstream of the filter 104. Since the aerosol is injected in adistributed manner across the air stream prior to encountering thespinning fan blades 162, the blades 162 more thoroughly mix the aerosolso that the air distributed inside the plenum 128 of the housing 102 hasa much more uniform distribution of aerosol concentration than if onlyone point of aerosol injection (e.g., a single nozzle) was utilized.

The above described aerosol injection process ensures that the filter104 is uniformly challenged across its plan area with substantially thesame aerosol concentration. This uniform mixture beneficially ensuresthat the filter 104 can be accurately scan tested. To ensure the filter104 is being challenged with a uniform aerosol laden air mixture, it isimportant to conduct factory qualification testing in accordance withindustry accepted standards and test methods. An exemplary standard isIEST-RP-CC0034.2, HEPA and ULPA Filter Leak Tests, which requires thatthe airstream on the upstream side of the tested filter 104 be sampledin multiple locations and analyzed for uniformity. The standard setsparameters for the testing and pass/fail criteria. In one embodiment,during qualification testing of the fan filter unit 100, various methodsof injecting aerosol were trialed, but the methods described herein gavea consistent uniform air-aerosol challenging mixture.

Comparative Results

A first method of injecting aerosol used a simple single point injectinglocation at a center of an inlet of the fan module within a multi-portaerosol injector. This method gave inconsistent results, because theinjected aerosol stream followed inlet air streamlines to one side ofthe centerline of the fan module, and thus the aerosol was unevenlydistributed inside the fan filter unit plenum. The highest challengeconcentration of the aerosol corresponded to a side of the fan module inwhich the aerosol streamlined. Moving the injection point of the aerosoleccentrically off center of the inlet of the fan module did not improvethe results. Although the injection point was directly over the centerof the inlet of the fan module, the aerosol still streamlinedinconsistently to various sides of the inlet of the fan module.

The next method to trial was to use the multi-port aerosol injector 108to evenly distribute the aerosol into the inlet of the fan module 106 byinjecting aerosol in multiple locations around the perimeter of the fanmodule 106, as discussed above. This method allowed the aerosol tofollow the streamlines of the inlet of the fan module 106, however,allowed multiple streamlines to be challenged with the same volume ofaerosol. This resulted in a much more uniform aerosol laden air mixtureupstream of the filter 104. The test results for this injection methodshowed beneficial results.

For example, using IEST-RP-CCO34.2 testing standards, a 100 mm pleatheight MEGALAM® panel filter was tested at: (i) 485 cubic feet/min, (ii)540 cubic feet/min, and (iii) 600 cubic feet/min with an upstreamaerosol concentration of approximately 50 micrograms/liter using 10sampling points that were located at various locations across theupstream face of the filter 104. The results respectively indicated: (i)an average concentration of 53 micrograms/liter at the sampling pointswith a standard deviation of 3 and a relative standard deviation of0.05, (ii) an average concentration of 49 micrograms/liter at thesampling points with a standard deviation of 3 and a relative standarddeviation of 0.07, and (iii) an average concentration of 56micrograms/liter at the sampling points with a standard deviation of 4and a relative standard deviation of 0.07, wherein the relative standarddeviation acceptance criteria is less than 0.20.

In another example using IEST-RP-CCO34.2 testing standards, a 50 mmpleat height MEGALAM® panel filter was tested at: (i) 485 cubicfeet/min, (ii) 540 cubic feet/min, and (iii) 600 cubic feet/min with anupstream aerosol concentration of approximately 50 micrograms/literusing 10 sampling points that were located at various locations acrossthe upstream face of the filter 104. The results respectively indicated:(i) an average concentration of 51 micrograms/liter at the samplingpoints with a standard deviation of 1 and a relative standard deviationof 0.03, (ii) an average concentration of 52 micrograms/liter at thesampling points with a standard deviation of 2 and a relative standarddeviation of 0.04, and (iii) an average concentration of 52micrograms/liter at the sampling points with a standard deviation of 2and a relative standard deviation of 0.04, wherein the relative standarddeviation acceptance criteria is less than 0.20.

Referring back to FIG. 3, an aerosol injector 308 may be positionedabove the fan module 306, for example, in the collar 304. The aerosolinjector 308 is coupled by a tube 346 to the aerosol access port 150(not shown in FIG. 3). The aerosol injector 308 and tube 346 aregenerally similar to the aerosol injector 108 and tube 346 describedabove with reference to FIG. 1. The tube 346 may be routed eithercompletely within the housing 302 or at least partially outside thehousing 302. In the embodiment depicted in FIG. 3, the tube 346 iscoupled to the aerosol injection ring 308, then runs external to thefilter housing 302 prior to entering the housing 302 through an opening310. The tube 346 may be sealed by a o-ring, gasket or caulk to thehousing 302 to form an air-tight seal at the opening 310.

FIG. 5 is a flow diagram of one embodiment of a method 500 for utilizinga roomside replaceable fan filter unit having an integral aerosolinjector ring. At step 502, a used filter is removed from the fan filterunit housing installed in a structure, such as a ceiling of a cleanroom, mini-environment, machine enclosure or other boundary of a cleanspace. At step 504, a replacement air filter is installed in housing. Atstep 506, a fan pulls air into housing and out through the replacementfilter. At step 508, an aerosol challenge is provided to the air flowingin the housing by the integral aerosol injector ring at a locationadjacent and upstream of an air moving blade of the fan. At step 510,the replacement filter is tested for leaks and/or filtration efficiencyby measuring the aerosol content at a location downstream of thereplacement filter.

While the foregoing is directed to embodiments of the invention, otherand further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

The invention claimed is:
 1. A method for utilizing a replaceable fanfilter unit comprising an integral aerosol injector ring, comprising:replacing a used filter from the fan filter unit with a replacementfilter from a roomside of the fan filter unit; pulling air into ahousing of the replaceable fan filter unit and out through thereplacement filter to the roomside by a fan module, the fan moduleupstream of the replacement filter; and providing an aerosol challengeat a location adjacent and upstream of the fan module.
 2. The method ofclaim 1, wherein providing the aerosol challenge comprises: injectingaerosol from an injector disposed in the housing.
 3. The method of claim1, wherein providing the aerosol challenge comprises: providing aerosolfrom an injector disposed in a collar disposed upstream of the fanfilter unit and configured to mate with ductwork.
 4. The method of claim1, wherein providing the aerosol challenge comprises: distributingevenly the aerosol into the inlet of the fan filter unit.
 5. The methodof claim 4, further comprising: injecting aerosol through multiple portsin the integral aerosol injector ring to multiple locations around theperimeter of the fan module.
 6. The method of claim 4, wherein integralaerosol injector ring is disposed upstream of an air moving blade of thefan module.
 7. The method of claim 1 further comprising: controlling aspeed of the fan module via an adjustment control located on adownstream side of the fan filter unit.
 8. The method of claim 1 furthercomprising: testing the replacement filter for leaks and/or filtrationefficiency.
 9. A method for utilizing a fan module comprising anintegral aerosol injector ring, comprising: forcing air through a filterhousing with a fan module disposed upstream a filter to the roomside ofthe filter housing; and providing an aerosol challenge at a locationadjacent and upstream of a fan blade in the fan module.
 10. The methodof claim 9, wherein the fan module is disposed in the filter housing.11. The method of claim 9, wherein providing the aerosol challengecomprises: injecting aerosol from an injector disposed in the filterhousing.
 12. The method of claim 9, wherein providing the aerosolchallenge comprises: providing aerosol from an injector disposed in acollar disposed upstream of the fan module and configured to mate withductwork.
 13. The method of claim 9, wherein providing the aerosolchallenge comprises: distributing evenly the aerosol into the inlet ofthe fan module.
 14. The method of claim 13, further comprising:injecting aerosol through multiple ports in the integral aerosolinjector ring to multiple locations around the perimeter of the fanfilter unit.
 15. The method of claim 13, wherein the integral aerosolinjector ring is disposed upstream of an air moving blade of the fanmodule.
 16. The method of claim 9 further comprising: controlling aspeed of the fan module via an adjustment control located on adownstream side of the housing.
 17. The method of claim 9 furthercomprising: testing the replacement filter for leaks and/or filtrationefficiency.